Thursday, May 16, 2013

New paper finds climate models are getting worse rather than better

A paper published today in Geophysical Research Letters finds that the latest climate models are performing even worse than the earlier generations of climate models in predicting "both the mean surface air temperature as well as the frequency of extreme monthly mean temperature events due to climate warming." The author hypothesizes the reasons for this are that attempts in the latest generation of models to reproduce observed changes in Arctic sea ice are causing "significant and widening discrepancy between the modeled and observed warming rates outside of the Arctic," i.e. they have improved Arctic simulation at the expense of poorly simulating the rest of the globe. The paper adds to hundreds of other peer-reviewed papers demonstrating the abject failure of climate models.

Abstract: Climate change simulations are the output of enormously complicated models containing resolved and parameterized physical processes ranging in scale from microns to the size of the Earth itself. Given this complexity, the application of subjective criteria in model development is inevitable. Here we show one danger of the use of such criteria in the construction of these simulations, namely the apparent emergence of a selection bias between generations of these simulations. Earlier generation ensembles of model simulations are shown to possess sufficient diversity to capture recent observed shifts in both the mean surface air temperature as well as the frequency of extreme monthly mean temperature events due to climate warming. However, current generation ensembles of model simulations are statistically inconsistent with these observed shifts, despite a marked reduction in the spread among ensemble members that by itself suggests convergence towards some common solution. This convergence indicates the possibility of a selection bias based upon warming rate. It is hypothesized that this bias is driven by the desire to more accurately capture the observed recent acceleration of warming in the Arctic and corresponding decline in Arctic sea ice. However, this convergence is difficult to justify given the significant and widening discrepancy between the modeled and observed warming rates outside of the Arctic.